Dams and levees are subject to erosion caused by steady-state and transient-state hydraulic loads exceeding critical velocities and critical shear stresses. Appropriate test methods have not been available to measure erodibility indices, such as erosion rate, critical shear stress, water overtopping critical velocity, water over-washing cyclical critical velocity, surface roughness, and threshold resistance to erosion initiation.
Conventional testing devices, such as laboratory flumes or on-site field flumes and the like, require samples of soil to be extracted from the surface and physically placed in an erosion testing device. The soil structure and shear strength properties are inadvertently altered, even if utmost attention is given to retrieving an “undisturbed” sample. If vegetative cover is to be tested in addition to the soil surface, either the vegetation must be artificially grown in a flume or the soil and root structure is significantly disturbed during sample retrieval and preparation. Existing laboratory or field testing devices are unable to address disparities between as-tested samples and in-situ samples.
Field plots for erosion testing, typically used in agronomy research, provide more accurate erodibility indices and hydraulic indices since this type of field testing is conducted in-situ. However, field plots are unable to vary overflow flow rate, velocity, or depth. Their purpose is to research inter-rill and rill erosion caused by rainfall intensity and runoff parameters. Field plots are not man-portable or transportable.
Select embodiments of the present invention enable on-site erodibility testing on surfaces having a wide variety of textures, from bare soil surfaces, to graminaceous or herbaceous vegetated surfaces often found on dams and levees, to geo-synthetic turf reinforcement mat overlays. Select embodiments of the present invention facilitate erosion testing beyond conventional tests on bare soil surfaces. Select embodiments of the present invention may be employed on bare soil, fissured soil, root clumps, and other real-life heterogeneous surface conditions. Select embodiments of the present invention replicate laboratory hydraulic flume experiments, correlating laboratory results to in-situ test results.
Select embodiments of the present invention provide variable hydraulic loads on a test plot while addressing compatibility issues arising from off-site versus on-site test results by controlling on-site hydraulic loading parameters much as is done in a laboratory. Further, there are no sampling compatibility issues because a sampled plot is a test plot enclosed within the test configuration.
Further, select embodiments of the present invention may be employed to test dam and levee armoring products such as turf reinforcement mats by placing on a mat similar to the way employed on natural soil.